Lapping machine



July 12, 1960 Filed Oct. 26, 1956 M. LIPKINS 2,944,375

LAPPING MACHINE 2 Sheets-Sheet 1 INVENTOR Mom'av LIP/(INS WA 5 h k ATTO R N EY July 12, 1960 I M. LlPKlNS 2,944,375

LAPPING MACHINE cs-Sheet 2 Filed Oct. 26, 1956 INVENTOR Max? ro/v Z /PK/NS ATTORNEY LAPPING MACHINE I V Morton Lipkins, 3 Nemeth St., Malverne, NY.

Filed lDct. 26, 1956, Ser. No. 618,650 17 Claims. 01. 51-117 States Patent applying a supplementary off-center pressure or weight series of article-retaining recesses arranged in a circle is disposed between the lapping rings for holding the articles in a pattern and moving the articles between the lapping surfaces. The weight of the top plate is carried by the articles, which develops the lapping pressure at the top and bottom faces of the' articles. The center of the article-ret-ainingnest is shifted inan orbit relative to the lapping plates,.and the nest is thus caused to translate in the same orbit; and in addition there is imparted a rotation of the nest about its center. The nest is free to assume this rotation. The articles carried by the nest thus move in complex paths between the lapping surf-aces.

A lapping compound is supplied or an abrasive is imbedded in the lapping surfaces. The top and bottom faces of the articles retained by the nest are progressively lapped to the required degree of parallelism, thickness, flatness and finish.

A serious difliculty in the operation of this well known type of machine results from the action of the lapping compound on the lapping faces in addition to the abrasion of the articles being finished. That is to say, the operation of the machine not only laps the articles being processed, but the compound also acts on the lapping surfaces themselves. The lapping surfaces progressively depart from their initially fiat condition and are deformed. Much effort has been devoted to meet the problem of preserving the original substantially flat condition of the lapping surfaces, but so far as I know, this type of lapping machine is commonly regarded as having the inherent characteristic of causing deformation of the lapping surfaces after even moderate'periods of operation.

Accordingly, an object of this invention is to improve the foregoing type of lapping machine, by greatly reducing the deformation of the lapping faces incidental to the lapping operation. Expressed otherwise, an object of this invention is to improve such machines, for greatly prolonging the period of operation without requiring shutdown for refacing the lapping surfaces of the lapping plates.

As an approach to the problem, I considered the pressures that are developed between the articles and the plates at different regions through which the articles move in complex paths. At any instant, the articles near the center of the lapping plates have more pressure ap plied to them and they, in turn, apply more pressure to the lapping plates, than the articles momentarily near the periphery of the lapping plates. When the articles inter change their relative positions later in the lapping operation, the relative amounts of pressure also reverse, as to ice the articles. I found the differences in pressures account for virtually all of the uneven wear of the plates. A further object of the invention, accordingly, is to devise mechanisms for improving the uniformity of pressure applied to each article by the top plate and thereby to the bottom plate as each article moves to its various positions in its complex path, particularly with regard to the extreme positions nearest to and farthest from the center of the lapping plates. This phase of the problem involved special difficulties because of the complex motions traveled by the articles in the-known lapping machines.

In achieving the foregoing purposes, I devised ways of to that part of the top lapping plate which at each instant was applying a relatively light force to the outermost article in the article-carrying nest, constantly shifting the point ofapplication of force in dependence on the travel of each successive article in the series of articles reaching the position farthest from the center of the lapping plates.

Such mechanisms yielded great gain in respectto the useful life of the lappingsurfaces in the improved machines. The article holder or nest has a rotation relative to the lapping plates in the improved machine (in addition to the orbital motion of the center of the nest). I discovered that this rotation can be controlled by the amount of supplementary force applied to the top lapping plate. With greater or less applied off-center force, it is possible to control the speed and direction of progressive rotation of the article carrier or nest relative to the lapping plates and with a critical, empirically determined force, that relative rotation can be arrested. Optimtnn results are obtained with slow rotation of the nest relative to the lapping plates.

By applying a supplementary force to the top lapping plate in the embodiments of the invention hereinalter described in detail, I am able to greatly extend the useful life of an initially fiat lapping surface on each of the lapping plates, before it becomes necessary for its surface to be refinished and corrected. Additionally, I am able to obtain more perfect products by greatly retarding the relatively rapid progressive deformation of the lapping surfaces in known machines.

Certain other objects and features of novelty will be noted in the following description of two illustrative em bodirnents of the invention shown in the accompanying drawings forming part of the present specification. In the drawings:

Fig. 1 is a vertical cross section of an illustrative em.- bodiment of the invention, and Fig. 2 is a top'pl'an view, partly in section, of the embodiment in Fig. 1;

Fig. 3 is a vertical cross section of another embodiment of the invention, and Fig. 4 is a top plan view thereof.

Referring now to Fig. 1 there are shown a pair of lapping plates in the form of rings 10 and 12 having lapping surfaces 10a and 12a that are flat, to a close approximation. These lapping rings are stationary, and they are held against relative rotation by a pair of L-shaped arms 14 extending from the lower ring 12 and into a pair of diametrically opposite eyes 16 extending radially from the upper lapping ring 10. An article carrier or so-called nest 18 is disposed between the confronting parallel spaced-apart lapping faces of lapping rings 10 and 12,

- nest 18 acting to hold a series of articles 20 distributed in a circular pattern. The articles 2!) are received in recesses 22 formed in nest 18, the center of the nest being off-set from the center of the rings. In Fig. 1, a drive about a fixed shaft 66, which is displaced laterally from the common axis of rings 50 and 52.

It will be recognized that, as shaft 58 rotates and causes rotation of rings 50 and 52, nest 60 will also rotateabout its fixed shaft 66. The rotation of rings 50 and 52 and of nest 60 causes each article-retaining recess to move from the innermost position represented at the left of Fig. 3 to the outermost position represented at the right of Fig. 3, thatis, in the same type of combined orbital'and rotational path relative to the plates 50 and 52 a; was achieved by the different mechanism in Figs. 1 an 2.

The rotation of the system of elements 50, 52 and 60 in Figs. 3 and 4 gives rise to certain important advantages. For example, it is now quite easy to apply a supply of lapping compound by means of a nozzle 68 directed inside ring 50, the compound reaching a spinning portion of nest 60 to be thereby distributed centrifugally all over the nest 60 and the lapping surfaces.

Similar to the condition existing in Fig. 1, it is clear that in Fig. 3 a relatively large force A is applied to the innermost article 64 in contrast to the relatively small force represented by the smaller arrow B and applied to-the outermost article 64, at the right of Fig. 3. This is because article 64 at the left of'Fig. 3 is considerably nearer to the center of gravity of ring 50 than article 64 at the right of Fig. 3 which is relatively remote from the center of mass of ring 50. Similarly, progressively decreasing forces developed by the weight of ring 50 are applied to the circularseries of articles betweenthe innermost article 64 and the outermost article 64 of the circular series.

Using reasoning developed in connection with Fig. 1 a supplementary weight is applied in Fig. 3. Weight 70, carried by shaft 72 and bearing on wheel 74, applies the supplementary force at an ofi-center portion of lapping ring 50, along the radius through the outermost article 64 of the circular series of articles carried by nest 60. This supplementary force has the effect of compensating for the unequal Weight distribution of ring 50 alone, and acts to achieve prolonged life of the lapping surfaces. I

Shaft '72 is vertically fixed in an arm 78 that is pivoted to a fixed support 80 disposed at one side of the lapping rings 50 and 52. This arm 78 also provides a fixed support for shaft 66. Arm 78 is formed witha fork at its right-hand extremity so that it resists any tendency that there might be for shafts 66 and 72 to shift, and additional' supplementary stilfening structure (not shown may be provided.

Detailed description of the operation of the apparatus in Figs. 3 and 4 appears to be unnecessary. Briefly, shaft 72 remains stationary and wheel 74 is at all times off center, in the direction of that article 64 which is in the outermost position relative to the axis of lapping rings 50 and 52, regardless of which article 64 assumes that position. This is true whether nest 60 rotates as fast as or at a different rate than this rotary speed of rings 50 and 52, Each of the articles is caused to move in its own complex path so as to be lapped during the rotation of lapping discs 50 and 52. The paths of articles 64 may be almost simple radial strokes relative to the lapping rings, back and forth over the lapping faces, or they may be similar to cycloidal paths relative to the lapping surfaces. The particular path that results is controlled in large measure by the amount of weight employed on shaft 72; and the optimum amount of weight, empirically determined, will produce the longest useful life of the lapping surfaces without requiring corrective resurfacing -What I claim is:

1. :In combination, an upper plate and a lower plate having confronting lapping surfaces in spaced-apart horizontal planes, a nest between said lapping surfaces, said nest having means for holding articles to be lapped in a circle extending to opposite sides of the center of said upper plate and at dilferent distances from the periphery thereof, means for effecting relative motion between the nest and the pair of plates such that the center of the nest has relative shifting motion in an orbit, carrying the articles successively to relatively retracted and relatively projected positions, and a supplementary forceapplying means disposed to act continuouslyon the upper plate toward the lower plate at the side thereof adjacent to the successively projected portions of the nest.

2. A lapping machine including a lapping ring having a fiat lapping surface, a nest having a series of recesses arranged in a circle for retaining articles at distributed positions in engagement with the lapping surface of said ring, means enforcing orbital shifting of the center of the nest in relation to the ring so that certain of the recesses in the nest move inward radially relative to thev ring while others move to relatively projected positions radially, said ring being heavy and its weight inherently. applying unequal pressures to the articles at-their respectively different distances from the center of the ring, and means disposed at a fixed distance from the center of said circle for applying a supplementary pressure to the successively different portions of the ring adjacent the successively radially projected nest recesses during the orbital motion of the nest relative to the lapping ring.- 3. A heavy lapping machine including a lapping ring having aflat bottom face, a nest having a series of recesses extending in a circle for retainingarticles in distributed positions in engagement with the lower lapping. surface of said ring, said circle extending about the center of said ring, means enforcing a relative orbital shift-. ing of the nest relative to the ring so that certain of the recesses in the nest move radially inward relative to the. ring while others move to relative radially projected positions, and means for applying a supplementary downward force to a portion of the ring adjacent the radially projected nest recesses during the orbital motion of the nest relative to the lapping ring. 4. In combination a lapping ring having a substantially flat horizontal bottom lapping surface, a nest having a series of recesses for retaining articles, said article-re. taining recesses being disposed in a circle about a center, a crank for shifting the nest in a circular orbital path about the center of the lapping ring, and the orbital shifting motion causing certain of the recesses gradually to move from intermediate positions toward radially inward positions relative to the center of the ring while at the same time causing other recesses to move progressively outward relative to the center of the ring, and means rotated with and by said crank for applyingv a supplementary force to the lapping ring continuously at the side thereof where the outermost article-retaining recesses are shifted.

. 5. Lapping apparatus including a lapping ring, means for rotating the lapping ring about its center, said lap-' ping ring having a flat-bottom lapping surface disposed horizontally, a nest having a circular series of .article-retaining recesses disposed below said lapping ring and with the center of the circle of recesses being offset relative to. the center of the ring and the circle of recesses extend-- ing about the center of the lapping ring eccentrically thereof, said lapping ring causing said nest to rotate, a

' 9 means being efiective to maintain said force applying means continuously in position required to compensate as aforesaid.

16. The method of lapping articles, including the steps of producing relative movement in an orbital path between the bottom lapping surface of a lapping member and a series of articles in contact therewith, subjecting the articles to the weight of the lapping member, the orbital path of relative movement causing the articles to shift in position to opposite sides of said lapping member and to different distances from the center thereof and the articles being thereby subjected unequally to the weight of the lapping member, and further imposing supplemental downward force on the lapping member at the side thereof where the successive relatively lightly loaded articles pass, for compensating approximately for the disparity of weight distribution of the lapping member against the articles.

17. A lapping machine including a heavy lapping plate having a lower lapping surface, meansifor maintaining a series of articles in contact with said lower lapping surface, means producing relative movement between said lapping plate and the first-mentioned means, the path of relative movement including positions of the articles that are relatively retracted and relatively projected with respect to the center of the lapping plate, said plate being arranged to rest on said articles, and said plate distributing its weight unequally among the articles in dependence on their relative retracted and projected positions, means for applying supplementary downward force to said plate arranged to compensate approximately for the disparity in the distribution or the weight of the plate among the articles, and means coordinating the application of supplementary force with said means for producing relative movement, said coordinating means maintaining the application of supplementary force by said applying means in position to efiect compensation as aforesaid.

References Cited in the file of this patent UNITED STATES PATENTS 1,541,001 Searles June 9, 1925 1,541,865 Smith June 16, 1925 2,398,906 McCain Apr. 23, 1946 2,518,501 Snyder Aug. 15, 1950 2,782,571 Hanson Feb. 26, 1957 

